Electro-hydraulic servo-distributor

ABSTRACT

An electro-hydraulic servo-distributor comprising a primary or pilot stage having a drive means constituted by a magnetic circuit which comprises two parallel polar cores, and two rectilinear magnets parallel to the cores and connected magnetically to one end of the cores by at least one metal plate. Two control coils are wound around the cores and a movable plate assembly is arranged opposite the other ends of the polar cores, forming therewith equal air gaps. The arrangement of the different components of the magnetic circuit is such that the flux produced by the control coils and the flux of one of the magnets pass across the corresponding air gap in the same direction, while the flux produced by the other magnet pass across the other air gap in the opposite directions. A support member is provided with a central part on which the movable plate assembly is fixed, and two lateral torsion rods which are each terminated by a lateral portion are engaged in the fixed structure of the servo-distributor. The support member also carries in its central part a hydraulic closure member which is substantially perpendicular to the plate assembly and which is intended to close according to the direction of magnetic turning moment to which the movable plate assembly is subjected, one or the other of two jets which are supplied with a hydraulic fluid, by a secondary or hydraulic stage controlling flow or controlling pressure.

United States Patent [1 1 Lucien [4 1 July 11, was

[ 1 ELECTRO-HYDRAULIC SERVO-DISTRIBUTOR [76] Inventor: Rene Lucien, 56, Boulevard Maillot,

92200 Neuilly sur la Seine, France [22] Filed: Dec. 27, 1973 [21] Appl. No.: 428,766

[30] Foreign Application Priority Data Dec. 29, 1972 France 72.47007 [52] US. Cl. 137/625.62; 251/137; 137/82 [51] Int. Cl..... F15c 3/02; Fl6k 11/07; G05d 16/20 [58] Field of Search 137/625.62, 82, 625.61,

Primary Examiner-Martin P. Schwadron Assistant ExaminerRobert J. Miller [5 7 ABSTRACT An electro-hydraulic servo-distributor comprising a primary or pilot stage having a drive means constituted by a magnetic circuit which comprises two parallel polar cores, and two rectilinear magnets parallel to the cores and connected magnetically to one end of the cores by at least one metal plate. Two control coils are wound around the cores and a movable plate assembly is arranged opposite the other ends of the polar cores, forming therewith equal air gaps. The arrangement of the different components of the magnetic circuit is such that the flux produced by the control coils and the flux of one of the magnets pass across the corresponding air gap in the same direction, while the flux produced by the other magnet pass across the other air gap in the opposite directions. A support member is provided with a central part on which the movable plate assembly is fixed, and two lateral torsion rods which are each terminated by a lateral portion are engaged in the fixed structure of the servo-distributor. The support member also carries in its central part a hydraulic closure member which is substantially perpendicular to the plate assembly and which is intended to close according to the direction of magnetic turning moment to which the movable plate assembly is subjected, one or the other of two jets which are supplied with a hydraulic fluid, by a secondary or hydraulic stage controlling flow or controlling pressure.

6 Claims, 7 Drawing Figures ELECTIRG-IIYDRAIULIC SERVO-DISTRIBUTOR The present invention concerns an electro-hydraulic servo-distributor which can be used in particular in a braking regulating system. More precisely, the invention concerns two alternative forms of servodistributor, one which can be used for controlling the flow of a hydraulic fluid, so as to deliver a flow which is proportional to an electrical control current, and the other concerning pressure control and delivering a pressure which is proportional or inversely proportional to the electrical control current.

The servo-distributor according to the invention is characterized in that it comprises a primary or pilot stage whose drive means is formed by a magnetic circuit which comprises two parallel polar cores, two rectilinear magnets parallel to said cores and connected magnetically to one end of the cores by means of at least one metal plate, two control coils wound around said cores, a movable metal plate assembly arranged opposite the other ends of the polar cores, forming therewith equal air gaps, the arrangement of the different components of the magnetic surface being such that the flux produced by the control coils and the flux of one of the magnets pass across the corresponding air gap in the same direction, while the flux produced by the control coils and the flux of the other magnet pass across the other air gap in opposite directions, a support member provided with a central part on which the movable plate assembly is fixed, and two lateral torsion rods which are each terminated by a lateral portion engaged in the fixed structure of the servo-distributor, said support member also carrying in its central part a hydraulic closure member which is substantially perpendicular to the plate assembly and which is intended to close, according to the direction of the magnetic turning moment to which the movable plate assembly is subjected, one or the other of two jets which are supplied with hydraulic fluid, by a secondary or hydraulic stage controlling flow or controlling pressure.

In a particular embodiment of the invention, the two lateral sectors of the support member are locked on said fixed structure by means of screws or the like, with the interposition of spacer members of calibrated thickness.

By virtue of such features, the active air gaps between the plate assembly and the polar cores, which air gaps are of the order of some tenths of millimeters, can be produced with a high degree of precision and a high degree of symmetry. In most cases the air gaps are produced in known motor-couples by a regulating operation which is always difficult to, perform. In the case of the present invention, these air gaps are produced directly upon assembly, without any regulation, because their thickness depends only on three dimensions which can be achieved with a high degree of precision by plane rectification, namely the thickness of the heads of the polar cores, the thickness of the movable plate assembly and the thickness of the spacer members. Moreover, symmetry of the air gaps can also be ensured by taking care to use for the same servodistributor apparatus, polar cores on the one hand and spacer members on the other hand which are part of a single rectification batch and whose height is then the same, to within a micron.

Other advantages and features of the invention will be apparent from the following description of several embodiments, with reference to the accompanying drawings, in which:

FIG. l is a view in cross-section ofa first embodiment of a servo-distributor comprising a pilot stage and a secondary flow control stage;

FIG. 2 is a plan view of a support member forming part of the movable assembly of the pilot stage of FIG.

FIG. 3 is a view in cross-section taken along line III- III in FIG. ll;

FIG. 4 is a view similar to that of FIG. )1, but in which the secondary stage serves for controlling pressure;

FIG. 5 is a graph which shows the working pressure/supply pressure characteristics, in dependence on the control current, corresponding to the servo-distributor of FIG. 4;

FIG. ti is a view of an alternative embodiment of the servo-distributor of FIG. l; and

FIG. 7 is a graph which shows the working pressure/supply pressure characteristics, in dependence on the control current, corresponding to the servo-distributor of FIG 6.

Referring to FIG. l, a first embodiment of the servodistributor of the invention comprises a primary or pilot stage II, and a secondary flow control stage 2. The secondary stage is of conventional construction and will therefore not be described hereinafter.

The drive means of the pilot stage is a magnetic circuitcomprising two cylindrical polar cores 3 and 3 on which are respectively wound two coils and 4' which are supplied with a control current carried by conductors 5, two rectilinear magnets and 6 which are parallel to the cores 3 and 3, a metal plate 7 magnetically connecting one end of the magnets 6 and 6 to the ends of the polar cores opposite heads 8 and 8, an annular metal plate 9 which is connected to the other ends of the magnets and which extends to a position below the heads 8 and 8 of the polar cores, and finally a movable plate assembly 10 formed by a flat elongate plate which extends below the heads and 8 and forms therewith equal air gaps llll and II.

As shown in FIGS. I and 2, the plate assembly M) is fixed to the central part 12 of a support member 113 which is clearly shown in FIG. 2. The support member also comprises two lateral sectors 14'- and H41 which are respectively attached to the central part 112 by means of two cylindrical portions 15 and R5 of relatively small diameter. The support member 13 is made in one single piece. As can be seen from FIG. 3, the two lateral sectors are secured to a fixed plate assembly 16 by means of bolts 117 with interposed spacer members 18 and 118.

The central part 12 of the member 113 also supports a hydraulic closure member 19, the end of which is positioned between the apertures of two jets 2t) and 203' which are supplied with hydraulic fluid from an inlet aperture 21 connected to a source of hydraulic fluid (not shown). The jets are supplied with fluid through holes 22 and 22 of relatively small diameter, protected by a filter 23. The return of the fluid to an outlet aperture 24 connected to the source, is through the secondary stage 2, along the path indicated by arrows. Depending on the position of the slide 25 in the bore 26, the fluid issuing from the jetsflows either to the outlet aperture 24 or to one of the working apertures 27 and 27.

As shown in FIG. 1, the fluxes 28 and 29 which are respectively produced by the magnet 6 and the coils 4 and 4 pass across the air gap 11 in opposite directions, while the flux 28' produced by the magnet 6' and the flux 29 pass across the air gap 1 l in the same direction. There is therefore a subtraction of fluxes in the first case, and an addition of fluxes in the second case, so that a magnetic turning moment is applied to the plate assembly 10. This moment tends to cause a pivotal movement of the plate assembly, and thereforethe central part 12 of the member 13, about its horizontal median axis, so as to apply the closure means 19 against one or other of the jets 20 and 20'. Because of the engagement of the sectors 14 and l4" on the plate member 16, the cylindrical portions 15v and 15 are subjected to resilient deformation and. apply a restoring moment which tends to return the central part 12 and thus the plate assembly l which is fixed therewith, to their equilibrium position in which the' plate assembly again Iies parallel to the end faces of the heads of the polar cores.

The jets, which are usually made of steel, are engaged in a support 30 of the same nature which is itself engaged in the body 31 of the apparatus, which is made of light alloy.

The jets 20 and 20' are held in gripped relation in their support 13 at all temperatures, because of the uniform nature of the materials, which makes it possible to provide a grip which is sufficiently weak to permit easy regulation, and to prevent subsequent disturbance of the regulation in the event of loss of grip, due to differential heat expansion.

This also causes the distance between the plate assembly l0 and the jets 20 and 20' in dependence on temperature to be kept constant, because of the uni form nature of the materials used.

The gripping of the support 30 in the body 31 is sufficient to be maintained at the heighest temperature which is encountered in use.

The above-described servo-distributor has the following advantages over conventional motor-couples:

construction of the magnetic circuit and the mode of suspension of the movable plate assembly are particularly simple.

as stated above, the air gap between the plate assembly and the heads of the polar cores is produced di rectly when the components are assembled, without any necessity for regulation.

the arrangement of this circuit makes it possible to separatethemovable assembly l0, 13, 19 of the pilot assembly which is in the oil, from the control coils 4 and 4' which are preferably left in air. The shape of the plate member 16 which forms the separation between these two parts, makes it possible for it to withstand a high internal hydraulic pressure.

FIG. 4 shows a servo-distributor for controlling a pressure, and using the same pilot stage as the servodistributor shown in FIG. 1, for controlling a flow rate. The actuation pressures supplied by the pilot stage act in chambers 32 and 32 on two equal annular crosssectional areas of the distribution slide 25. The working pressure in the chamber 33 which is connected to'the working aperture 34 is re-injected, by way of a passage 35 in the slide 25, into a chamber 36 in whichit acts on the correspondingcross-sectional area of the slide. A chamber 37 which is symmetrical with respect to the chamber 36 is kept in permanent communicationwith the return aperture 38, by way of a passage 39 in the distribution slide.

This arrangement makes it possible to produce a working pressure which is proportional to the difference in the control pressures in the chambers 32 and 32'. Regulation of the pilot stage and its direction of operation are such that the pressure in the chamber 32 is always higher than or equal to that in the chamber 32. When these pressures are equal, the working pressure is equal to the return pressure. When the pressure in the chamber 32 is higher than that in the chamber 32, the working pressure is proportional to said pressure difference, the proportionality factor being equal to the ratio of the annular cross-sectional areas of the chambers 32 and 32', to the cross-sectional area of the end of the slide which extends into the chamber 36.

The particularity of the above-described arrangement, with respect to the arrangement of known apparatuses, lies in the adoption of symmetrical control chambers, which makes it possible to produce a working pressure which preserves a stable level with respect to the return pressure, irrespective of the value of the return pressure, provided that it remains low relative to the supply pressure. 7

When the supply pressure varies, the characteristics of working pressure-control current in dependence on the supply pressure are as shown in the graph in FIG. 5,.which corresponds to an apparatus so regulated that the working pressure is inversely proportional to the control current. In the graph in FIG. 5, the ratio i/i of the actuation current to the maximum current is entered in the abscissae, while the ratio Pu/Pa of the working pressure to the supply pressure is entered in the ordinates,;and the diagram shows the curves representing variation corresponding to supply pressures which are respectively equal to 100, 80, 50 and 10 percentof the maximum supply pressure.

FIG. shows a second embodiment of the servodistributor for controlling a pressure, which differs from' the above-described pressure control embodiment only in the structure of the distribution slide 25. The slide 25 comprises a passage 40 which brings the chamber 37 into communication with the supply aperture 41, whereas in the above-described embodiment, the chamber 37 communicated with the return aperture'38. V

This gives the characteristics of working pressure/- control current which are as shown in FIG. 7, in dependence on the supply pressure. FIG. 7 corresponds, as above, to the primary stage being so regulated that the working pressure is inversely proportional to the control current. In this c is the working pressure is not sensitive to thereturnl pressure, for small variations in the return pressure relative to the supply pressure.

Another original feature of the apparatus according .to the invention is that the characteristics of. FIGS. 5

and 7 are achieved as'desired, by using one of the two types of distributionrslides described, and by consequenti'ally regulating the primary stage; in the case of FIG. 6, it is the pressure in the chamber 32 which is higher than' or equal to that in the pressure 32. One or other of these types of characteristics can be achieved,

according :tothe kind of use, a possible use being braking regulating systems.

I claim:

1. An electro-hydraulic servo-distributor comprising a primary or pilot stage incliiding a drive means constituted by a magnetic circuit which comprises two parallel polar cores, two rectilinear magnets parallel to said cores and connected magnetically to one end of the cores by means of at least one metal plate, two control coils wound around said cores, a movable metal plate assembly arranged opposite the other ends of the polar cores, forming therewith equal air gaps, the arrangement of the different components of the magnetic circuit being such that the flux produced by the control coils and the flux of one of the magnets pass across the corresponding air gap in the same direction, while the flux produced by the control coils and the flux produced by the other magnet pass across the other air gap in opposite directions, a support member provided with a central part on which is fixed the movable plate assembly and two lateral torsion rods which are each terminated by a lateral portion engaged in the fixed structure of the servo-distributor, the support member also carrying in its central part a hydraulic closure member which is substantially perpendicular to the plate assembly and which is intended to close, according to the direction of magnetic turning moment to which the movable plate assembly is subjected, one or the other of two jets which are supplied with hydraulic fluid, by a secondary or hydraulic stage controlling flow rate or controlling pressure.

2. A servo-distributor according to claim 1, wherein the two lateral sectors of the support member are locked on said fixed structure by means of screws, with the interposition of spacer members of calibrated thickness.

3. A servo-distributor according to claim 2, wherein the screws are fixed in a plate member for ensuring a sealing action between the control coils which are in air, and the movable assembly formed by the plate as sembly, the support member and the closure member which are immersed in the hydraulic fluid.

4. A servo-distributor according to claim 1, wherein the jets are made of metal and are each engaged in a part made of the same metal, which is itself held in the body of the servo-distributor.

5. A servo-distributor according to claim 1, wherein the secondary stage comprises a distribution slide mounted slidably in a bore comprising a first annular chamber and a second annular chamber which are separate from each other and which are connected to the outlet of the jets, a third annular chamber connected to a working aperture, said third chamber communicating through a first passage in the slide with a first terminal chamber at one of the ends of the slide, a second terminal chamber at the other end of the slide communicating through a second passage in the slide with a return aperture, the regulation of the pilot stage and its direction of operation being such that the pressure in said first annular chamber is always at least equal to that of the second annular chamber.

6. A servo-distributor according to claim 1, wherein the secondary stage comprises a distribution slide mounted slidably in a bore comprising a first annular chamber and a second annular chamber which are separate from each other and which are connected to the outlet of the jets, a third annular chamber connected to a working aperture, said third chamber communicating through a first passage in the slide with a first terminal chamber at one of the ends of the slide, a second terminal chamber at the other end of the slide communicating through a second passage in the slide With the supply aperture, the regulation of the pilot stage and its direction of operation being such that the pressure in said first annular chamber is always at least equal to that of 

1. An electro-hydraulic servo-distributor comprising a primary or pilot stage including a drive means constituted by a magnetic circuit which comprises two parallel polar cores, two rectilinear magnets parallel to said cores and connected magnetically to one end of the cores by means of at least one metal plate, two control coils wound around said cores, a movable metal plate assembly arranged opposite the other ends of the polar cores, forming therewith equal air gaps, the arrangement of the different components of the magnetic circuit being such that the flux produced by the control coils and the flux of one of the magnets pass across the corresponding air gap in the same direction, while the flux produced by the control coils and the flux produced by the other magnet pass across the other air gap in opposite directions, a support member provided with a central part on which is fixed the movable plate assembly and two lateral torsion rods which are each terminated by a lateral portion engaged in the fixed structure of the servo-distributor, the support member also carrying in its central part a hydraulic closure member which is substantially perpendicular to the plate assembly and which is intended to close, according to the direction of magnetic turning moment to which the movable plate assembly is subjected, one or the other of two jets which are supplied with hydraulic fluid, by a secondary or hydraulic stage controlling flow rate or controlling pressure.
 2. A servo-distributor according to claim 1, wherein the two lateral sectors of the support member are locked on said fixed structure by means of screws, with the interposition of spacer members of calibrated thickness.
 3. A servo-distributor according to claim 2, wherein the screws are fixed in a plate member for ensuring a sealing action between the control coils which are in air, and the movable assembly formed by the plate assembly, the support member and the closure member which are immersed in the hydraulic fluid.
 4. A servo-distributor according to claim 1, wherein the jets are made of metal and are each engaged in a part made of the same metal, which is itself held in the body of the servo-distributor.
 5. A servo-distributor according to claim 1, wherein the secondary stage comprises a distribution slide mounted slidably in a bore comprising a first annular chamber and a second annular chamber which are separate from each other and which are connected to the outlet of the jets, a third annular chamber connected to a working aperture, said third chamber communicating through a first passage in the slide with a first terminal chamber at one of the ends of the slide, a second terminal chamber at the other end of the slide communicating through a second passage in the slide with a return aperture, the regulation of the pilot stage and its direction of operation being such that the pressure in said first annular chamber is always at least equal to that of the second annular chamber.
 6. A servo-distributor according to claim 1, wherein the secondary stage comprises a distribution slide mounted slidably in a bore comprising a first annular chamber and a second annular chamber which are separate from each other and which are connected to the outlet of the jets, a third annular chamber connected to a working aperture, said third chamber communicating through a first passage in the slide with a first terminal chamber at one of the ends of the slide, a second terminal chamber at the other end of the slide communicating through a second passage in the slide with the supply aperture, the regulation of the pilot stage and its direction of operation being such that the pressure in said first annular chamber is always at least equal to that of the second annular chamber. 